Use Runtime type instead of int32 in our Movie struct.

internal/data/movies.go

@@ -12,7 +12,10 @@ type Movie struct {
 	CreatedAt time.Time `json:"-"`
 	Title     string    `json:"title"`
 	Year      int32     `json:"year,omitempty"`
-	Runtime   int32     `json:"runtime,omitempty,string"`
-	Genres    []string  `json:"genres,omitempty"`
-	Version   int32     `json:"version"`
+	/*
+		Use the Runtime type instead of int32. Note that the omitempty directive will still work on this: if the Runtime field has the underlying value 0, then it will be considered empty and omitted -- and the MarshalJSON() method we just made won't be called at all.
+	*/
+	Runtime Runtime  `json:"runtime,omitempty,string"`
+	Genres  []string `json:"genres,omitempty"`
+	Version int32    `json:"version"`
 }